Résumé
In this paper, we propose an original method to embed the color information of an image in a corresponding compressed grey-level image. The objective of this work is to allow free access to the compressed grey-level image and give color image access only if you own a secret key. This method is made of three major steps which are the color quantization, the ordering and the DCT-based data hiding. The novelty of this paper is to build an indexed image which is, in the same time, a semantically intelligible grey-level image. In order to obtain this particular indexed image, which should be robust to data hiding, we propose an original K color ordering algorithm. Finally, the DCT-based data-hiding method benefits from the used of an hybrid JPEG coder which allows to compress images with a Word Wide Web standard format and in the same time proposes a data-hiding functionality.